This invention relates to compositions useful in and methods for cleaning, degreasing, stripping, solvating and/or removing residues and contaminants from manufactured articles and hard surfaces.
More particularly, this invention relates to compositions useful in and methods for cleaning, degreasing, stripping, solvating and/or removing residues such as oils, grease, dirt, flux, inks, coatings, photoresists, resins and polymers and contaminants from manufactured articles and hard surfaces such as, but not limited to metals, plastics, textiles, electronic devices, silicon wafers, mechanical devices or manufacturing equipment.
According to this invention, 4-carbon cyclic ether solvent mixtures with 3-alkoxy-3-methyl butanol, and optionally with alkaline materials or with other materials known to those skilled in the art can be used to replace highly ozone depleting materials such as chlorofluorocarbons (CFC), methyl chloroform, hydrochlororfluorocarbons (HCFC), or chlorinated solvents. There is an unexpected and broad level of solubility obtained for many varied cleaning applications by the use of the solvent mixtures which is not obtained by using a single component solvent system.
Four-carbon cyclic ether solvents of the disclosed invention correspond to the following formula: ##STR1## Where R.sub.1 and R.sub.2 can be independently hydrogen, or 1 to 8 carbon length alkyl, alkoxy or ether groups.
The disclosed 3 alkoxy 3 methyl butanol corresponds to the following formula: ##STR2## Where the OH group of the butanol can be attached to carbon position 1, 2 or 4, and R.sub.3 is hydrogen or 1 to 8 carbon length alkyl.
The optional alkaline material is any material known to those skilled in the art that would cause the pH of the solution to be greater than 6. Materials such as alkaline hydroxides, carbonates, bicarbonates, and silicates; and nitrogen containing materials such as amines, alkanolamines, quaternary ammonium hydroxides and amides can be used in the present invention. The alkaline hydroxides, carbonates, bicarbonates, and silicates are preferably those of the alkali or alkaline earth metals or the ammonium salts.
Other materials that can be added are one or more of the following materials: water, alcohols, esters, ethers, cyclic ethers, ketones, alkanes, terpenes, dibasic esters, glycol ethers, pyrollidones, or low or non ozone depleting chlorinated and chlorinated/fluorinated hydrocarbons.
The use of these disclosed mixtures is in response to concerns about ozone depleting materials, and toxicity concerns with non ozone depleting chlorinated materials. In September 1987, the United States and 22 other countries signed the Montreal Protocol on Substances that Deplete the Ozone Layer (the "Protocol"). The Protocol called for a freeze in the production and consumption of ozone depleting chemicals ("ODP's" or "ODC's") by the year 2000 for developed countries and 2010 for developing countries. In 1990 the United States enacted the Clean Air act mandating that the use of ozone depleting chemicals be phased out by the year 2000. In September 1991, the U.S. Environmental Protection Agency announced that ozone layer depletion over North America was greater than expected. In response to this announcement, President George Bush issued an executive order accelerating the phase-out of the production of ozone depleting materials to Dec. 31, 1995. More that 90 nations, representing well over 90% of the world's consumption of ODP's, have agreed to accelerate the phase-out of production of high ozone depleting materials to Dec. 31, 1995 for developed countries and Dec. 31, 2005 for developing countries pursuant to the protocol.
Historically fluorine and chlorine based solvents were widely used for degreasing, solvating, solvent cleaning, aerosol cleaning, stripping, drying, cold cleaning, and vapor degreasing applications. In the most basic form the cleaning process required contacting a part with the solvent to remove an undesired material, soil or contaminant. In solvating applications these materials were added to dissolve materials in such applications as adhesive or paint formulations.
Cold cleaning, aerosol cleaning, stripping and basic degreasing were simple applications where a number of solvents were used. In most of these processes the soiled part was immersed in the fluid, sprayed with the fluid, or wiped with cloths or similar objects that had been soaked with the fluid. The soil was removed and the part was allowed to air dry.
Drying, vapor degreasing and/or solvent cleaning consisted of exposing a room temperature part to the vapors of a boiling fluid. Vapors condensing on the part provided a clean distilled fluid to wash away soils and contaminants. Evaporation of the fluid from the part provided a clean part similar to cleaning the part in uncontaminated fluid.
More difficult cleaning of difficult soils or stripping of siccative coatings such as photomasks and coatings required enhancing the cleaning process through the use of elevated fluid temperatures along with mechanical energy provided by pressures sprays, ultrasonic energy and or mechanical agitation of the fluid. In addition these process enhancements were also used to accelerate the cleaning process for less difficult soils, but were required for rapid cleaning of large volumes of parts. In these applications the use of immersion into 1 or more boiling sumps, combined with the use of the above mentioned process enhancements was used to remove the bulk of the contaminant. This was followed by immersion of the part into a sump that contained freshly distilled fluid, then followed by exposing the part to fluid vapors which condensed on the part providing a final cleaning and rinsing. The part was removed and the fluid evaporated off the clean part. Vapor degreasers suitable in the above-described process are well known in art.
In recent years the art was continually seeking new fluorocarbon based mixtures which offered similar cleaning characteristics to the chlorinated and CFC based mixtures and azeotropes. In the early 1990's materials based on the compounds of HCFC began to appear. Three molecules in particular 1,1-dichloro-1-fluoro ethane (HCFC-141b), dichloro trifluoro ethane (HCFC-123), and dichloro pentafluoro propane (HCFC-225) were proposed as replacements for methyl chloroform and CFC blends. As more highly fluorinated materials these materials were less ozone depleting than current ODP's however these materials were weaker solvents and in order to properly clean required the use of co-solvents through the use of blends and azeotropes.
The art in the mid 1990's progressed as aqueous and semi-aqueous materials became the major choice of replacement for ODP's. Many of the materials developed and selected were materials that usually had lower toxicity, volatility and higher flash points than common solvents. The art generally developed along three basic type of cleaning materials. These materials were water insoluble organics, water soluble inorganics and water soluble organics.
The development of water insoluble cleaning agents as ODP replacements took many new art forms, disclosed in many countries. Typically this art included the predominant use of aliphatic and aromatic hydrocarbons, terpene hydrocarbons, and water insoluble esters. These products usually were good agents to clean and solvate organic contaminants, however they had drawbacks in that they were difficult to rinse with water and had little effect on ionic or inorganic residues. In addition, being water insoluble they were limited in their application and could not be diluted with water for spray applications.
The art of water soluble inorganic materials has been well known for years, usually in low technology applications where gross contaminant removal was desired. The art was upgraded in the last 10 years as work was done to create new mixtures that had solvating and cleaning efficacy in high technology applications where ODP materials were used. The bulk of the inorganic materials used were alkali metal salts (usually sodium or potassium) which included hydroxides, carbonates, silicates, phosphates, and bicarbonates. Many of the inorganic mixtures also included the use of surfactants and water soluble organic solvents to assist in the cleaning application. Cleaning agents of this art usually were inexpensive and found application in many non critical cleaning applications. The drawback of this art is that the mixture usually had solubility for a narrow range of contaminants, and in most cases was ineffective against tough contaminants. Other issues concerned the high pH required of the mixture to effectively clean, concern of possible alkaline residues left on the substrate due to inadequate rinsing, and short bath life due to consumption of the agent by the contaminant.
The art of water soluble organic materials as ODP replacements was the third and most flexible route chosen as replacement materials. Typically the art included materials such as alcohols, ethers, esters, glycol ethers and pyrollidones. Most of the formulations that have been disclosed utilized these materials either alone or in combination with other solvents, alkalinity agents and or water. Most of the alcohols, esters and ethers selected that were water soluble typically had low molecular weights that created flash point or volatility issues in the mixture. Glycol ethers were another choice, however toxicity concerns became an issue with ethylene based glycol ethers. The art in the 1990's tended to move to propylene based glycol ethers because of their lesser toxicity concern. These materials however were not as robust as cleaners as alcohols or ethylene based glycol ethers, and required selective formulation and/or higher concentrations of the materials. Pyrollidones were also used in the art, however their broad use was limited because of cost, toxicity concerns and the highly aggressive nature of the material to some substrate materials.
A major drawback of the water soluble materials was the constant balance that was required to make the formulation clean a broad range of contaminants. Typically materials and mixtures could be found that were effective on ionic or polar soils, but were not effective on non-polar soils or oils. In addition some water soluble materials were very aggressive to some substrate materials such as coatings and metals. Hence proper selection of water soluble base materials is a key parameter in obtaining effective cleaning mixtures that clean efficiently and exhibit superior results over a broad range of contaminants.
The present invention overcomes the problems and disadvantages that currently exist by providing a cleaning mixture and process for cleaning efficiently a broad range of soils, which exhibits superior properties or results over the previous materials, mixtures and methods. It is, therefore, an object of the invention to provide an efficient, cost-effective process for cleaning, degreasing, stripping, solvating and/or removing residues and contaminants such as oils, grease, dirt, flux, inks, coatings, photoresists, resins and polymers from manufactured articles.
The present invention achieves that object by providing solvents and solvent mixtures and methods for cleaning, degreasing, stripping, solvating and/or removing residues and contaminants such as oils, grease, dirt, flux, inks, coatings, photoresists, resins and polymers from manufactured articles and hard surfaces such as, but not limited to metals, plastics, textiles, electronic devices, silicon wafers, mechanical devices or manufacturing equipment, which may be suitable for use on an industrial scale.
According to this invention, novel cleaning compositions are provided which contain a mixture of materials that have been found to be synergistic in cleaning a broad range of soils and contaminants. The mixture contains one or more compounds from the family described as a four-carbon cyclic ether, known in the art as a tetrahydrofuran ring. Four carbon cyclic ether solvents of the invention correspond to the following formula: ##STR3## Where R.sub.1 and R.sub.2 can be independently hydrogen, or 1 to 8 carbon length alkyl, alkoxy or ether groups. Preferred compounds of formula I are water soluble and exhibit flash points greater than 100.degree. F. (ca. 38.degree. C.).
The second required compound of the mixture contains one or more compounds from the family described as a 3-alkoxy-3-methyl butanol and corresponds to the following formula: R.sub.3 ##STR4## Where the OH group of the butanol can be attached to carbon position 1, 2 or 4, and R.sub.3 is hydrogen or 1 to 8 carbon length alkyl. Preferred compounds of formula II are water soluble and exhibit flash points greater than 100.degree. F.
Other optional compounds are materials that can be added to a mixture of the compounds of Formula I and Formula II that will maintain the pH of the mixture at greater than 6. The optional alkaline material is any material known to those skilled in the art that would cause the pH of the solution to be greater than 6. Materials such as alkaline hydroxides, carbonates, bicarbonates, and silicates, preferably those of the alkali or alkaline earth metals or ammonium; and nitrogen containing materials such as amines, alkanolamines, quaternary ammonium hydroxides and amides can be used in the present invention. The preferred compounds of the cleaning compositions are nitrogen containing compounds that also contain one hydroxyl group.
Other optional materials that can be added are one or more of the following materials: water, alcohols, esters, ethers, cyclic ethers, ketones, alkanes, terpenes, dibasic esters, glycol ethers, pyrollidones, or low or non ozone depleting chlorinated and chlorinated/fluorinated hydrocarbons. Preferred compounds that can be added are water soluble and exhibit flash points greater than 100.degree. F.
The compositions may also be enhanced by one skilled in the art by adding buffering agents, surfactants, chelating agents, colorants, dyes, fragrances, indicators, inhibitors, and other conventional ingredients.
More specifically, the cleaning composition of the invention generally has a pH greater than 6.0, and contains effective amounts of the compounds of Formula I and Formula II.
Preferred compositions and methods for cleaning mixtures in accordance with this invention contain an effective amount of at least one compound of Formula I. In preferred embodiments, R.sub.1 and R.sub.2 are hydrogen or alkoxy groups containing from 1 to about 8 carbon atoms and, in a more preferred embodiment, the alkoxy groups contain from 1 to 3 carbon atoms. Specific examples of alkoxy groups containing from 1 to about 8 carbon atoms include methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, octoxy.
Examples of specific preferred 4-carbon cyclic ethers containing alkoxy groups, which can be used in the method of the invention, include tetrahydrofuran, tetrahydrofurfuryl alcohol, bis-hydroxymethyl tetrahydrofuran, tetrahydro-2-furanethanol, bis-hydroxyethyl tetrahydrofuran, tetrahydro-2-furanethanol, bis-hydroxypropyl tetrahydrofuran. Most preferred are tetrahydrofurfuryl methanol and bis-hydroxymethyl tetrahydrofuran.
In another preferred embodiment, R.sub.1 and R.sub.2, in Formula I are each, independently, hydrogen, alkoxy and/or ether groups containing from 1 to about 8 carbon atoms and, in a more preferred embodiment, the alkoxy and/or ether groups contain from 1 to 4 carbon atoms. Specific examples of alkoxy groups containing from one to 8 carbon atoms include methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, and octoxy. Specific examples of ethers are methoxy methyl ether, methoxy ethyl ether, methoxy propyl ether, methoxy butyl ether, ethoxy methyl ether, ethoxy ethyl ether, and ethoxy propyl ether. Most preferred are: tetrahydrofuran-2-methoxy ether, tetrahydrofuran-2,5-dimethoxy ether, tetrahydrofuran-2-methoxy ethyl ether, tetrahydrofuran-2-ethoxy ether, tetrahydrofuran-2,5-diethoxy ether and tetrahydrofuran-2-methoxy propyl ether.
Preferred compositions and methods for cleaning mixtures in accordance with this invention contain an effective amount of at least one compound of Formula II. In preferred embodiments, the OH group of the butanol can be attached to carbon position 1, 2 or 4, and R.sub.3 is 1 to 8 carbon length alkyl. In preferred embodiments, R.sub.3 is hydrogen or alkoxy groups containing from 1 to about 8 carbon atoms and, in a more preferred embodiment, the alkyoxy groups contain from 1 to 3 carbon atoms. Specific examples of alkoxy groups containing from 1 to about 8 carbon atoms include methoxy, ethoxy, propoxy, butoxy, pentoxy, hexoxy, heptoxy, octoxy.
Examples of specific preferred materials are 3-methyl-3-hydroxy-1-butanol, 3-methyl-3-methoxy-1-butanol, 3-methyl-3-ethoxy-1-butanol, 3-methyl-3-propoxy-1-butanol, 3-methyl-3-methoxy-2-butanol, and 3-methyl-3-methoxy-4-butanol. Most preferred is 3-methyl-3-methoxy-1-butanol.
In this embodiment, the solution may comprise from about 0.01 up to about 99.9% by weight of either compound of Formula I or Formula II.
Preferred compositions and methods for cleaning mixtures in accordance with this invention optionally contain effective amounts of materials that can be added to a mixture of the two above disclosed materials that will maintain the pH of the mixture at greater than 6. The optional alkaline material is any material known to those skilled in the art that would cause the pH of the solution to be greater than 6. Materials such as alkaline hydroxides, carbonates, bicarbonates, and silicates; and nitrogen containing materials such as amines, alkanolamines, quaternary ammonium hydroxides and amides can be used in the present invention. The preferred compounds of the cleaning compositions are nitrogen containing compounds that also contain one hydroxyl group. Most preferred are monoethanolamine, diethanolamine, triethanolamine, 1-amino-2-propanol, ethylenediamine, hexamethyldiamine, 1,3-pentanediamine, n-isopropyl hydroxylamine, and 2-methyl-pentamethylenediamine.
The materials of Formulas I and II useful as cleaning mixtures in accordance with this invention are soluble in various solvents, such as water, alcohols, aqueous inorganic hydroxides, esters, ethers, cyclic ethers, ketones, alkanes, terpenes, dibasic esters, glycol ethers, pyrrolidones, or low or non-ozone depleting chlorinated and chlorinated/fluorinated hydrocarbons. Thus, the composition or mixture utilized in the process of the invention, and which comprises one or more of the above-described compounds, may be dissolved in any one or more of the before-mentioned solvents as an additional component of the cleaning composition. The detailed description below provides a non-limiting disclosure of the additional components that may be selected. The compositions of the invention, thus, may also include one or more of the above-mentioned solvents. Aqueous and non aqueous solutions of tetrahydrofurfuryl alcohol, 3-methyl 3-methoxy-1-butanol and amines, alkaline agents containing 1 or more hydroxyl groups are preferred in the practice of the invention, but other solvents may be used in conjunction with those. The form the compositions are in when used for cleaning may vary from liquid at various temperatures, to vapor, to aerosol, or other dispersions appropriate for the components of the composition selected. Buffers, corrosion inhibitors and other additives may also be included in the cleaning compositions of the invention.
The material to be removed from a surface or cleaned by this invention can be any residue and contaminants such as oils, grease, dirt, flux, inks, coatings, photoresists, resins and polymers.
Specific examples of parts or articles cleaned by the process or compositions of this invention include manufactured articles and hard surfaces such as, but not limited to metals, plastics, textiles, electronic devices, silicon wafers, mechanical devices or manufacturing equipment.
Contacting an article with a cleaning composition according to the invention may be through a conventional process or means known in the art that includes but is not limited to: wiping; spraying; immersing; high pressure spray agitation; ultrasonic agitation; vapor degreasing; and soaking. The equipment to perform these processes is known in the art or can be devised from other fields where applying a composition to a solid surface is involved. The process may be conducted at ambient temperature or up to the boiling point of the selected cleaning composition. Generally, temperature ranges from about 32.degree. F. (0.degree. C.) to about 230.degree. F. (110.degree. C.) are used. The temperature used may also be determined by the selection of the manner of contacting the cleaning composition to the surface to be cleaned. The process is most commonly conducted at atmospheric pressure, but may be conducted at elevated pressure, in a vacuum, or at lower than atmospheric pressure conditions.
The part or article is contacted with the desired cleaning composition for a sufficient period of time to essentially remove the contaminant or remove the desired amount of the contaminant. The part or article can also be called a "surface" that is to be cleaned. Depending on the nature of the article and the use to which it will be put, it may not be necessary for every detectable trace of a contaminant to be removed from the surface. The contaminant may be any unwanted or undesired materials in contact with the substrate surface and may include is not limited to oils, grease, dirt, flux, inks, coatings, photoresists, resins and polymers, present in an amount ranging from a residue to a clearly visible amount.
It may, in most instances, be necessary or desirable to rinse the cleaning composition from the part or article with water or with one of the solvents listed above, or with any combination of water and solvents. One skilled in the art can devise numerous combinations of cleaning compositions and rinsing solutions from this disclosure and the known properties of the chemicals used. In addition, one skilled in the art can devise simple tests to determine the appropriate rinsing conditions for a cleaning composition selected. It is common in the art to select a rinsing solution that will effectively remove all of the cleaning agent or composition and allow the rinsing solution to dry from the part either through the use of moving air, heated air and/or natural evaporation. Compounds that affect the odor of a surface being cleaned, that inhibit the corrosion of the surface, or that act as a surfactant can also be added to the cleaning compositions or rinsing solutions and used in the cleaning methods.